1. Field of the Invention
This invention relates to oral alkanol free glycol based analgesic compositions containing high concentrations of benzocaine. More particularly, this invention relates to oral analgesic compositions in liquid and gel form having high potency and protected from microbiological degradation by a preservative agent which is a combination of methylparaben and phenylcarbinol.
2. Description of Related Art
An anesthetic composition comprising high concentrations of benzocaine is described in U.S. Pat. No. 5,446,063. The benzocaine is dispersed or suspended in an admixture of water and emollient vehicle and is not completely dissolved. Another benzocainie composition comprising high concentrations of benzocaine is described in U.S. Pat. No. 4,241,048. That patent discloses a composition containing benzocaine suspended in an essentially anhydrous carrier also containing a crystal growth suppressing agent. These prior art patents disclose the use of preservatives including methylparaben and propylparaben.
According to this invention, an oral analgesic glycol based composition which is anhydrous and alkanol free, containing high concentrations of benzocaine, is provided in liquid or gel form and which is protected from bacterial degradation by a preservative agent which is a combination of methylparaben and phenylcarbinol. The benzocaine compositions of the invention contain about 5 to about 20% by weight of benzocaine, based on the weight of the total composition. The amount of glycol based solvent system is about 40% to about 80% by weight based on the weight of the total composition when in liquid form, and about 40% to about 60% when in gel form. The glycol based solvent system contains about 80% to about 100% by weight of polyethylene glycol when in liquid form and in gel form, based on the weight of the glycol based solvent system, and advantageously up to about 20% by weight of a co-solvent for the benzocaine compatible with polyethylene glycol, based on the weight of the glycol based solvent system. The methylparaben component of the preservative agent can be about 0.05 to about 0.2% by weight of the total composition and the phenylcarbinol component of the preservative agent can be about 0.25 to about 0.5% by weight of the total composition. Co-solvents for the benzocaine compatible with polyethylene glycol are propylene glycol and glycerine.
The invention includes analgesic compositions in liquid form and in gel form and in regular strength and maximum strength. The regular strength forms contain about 7.5% to about 10% by weight of benzocaine and the maximum strength forms contain about 10% to about 20% by weight of benzocaine.
The liquid form of the invention can contain in addition to the benzocaine, the glycol based solvent system, and the preservative agent, sweeteners such as saccharin, flavoring agents such as spearmint and coloring agents.
The gel form of the invention contains in addition to the benzocaine, the glycol based solvent system, and the preservative agent, a thickening agent such as Carbomer 934 P brand of carboxy-vinyl polymer, and a co-solvent for the thickening agent such as gylcerin. The thickening agent can range from about 2% to about 2.5% by weight and the co-solvent for the thickening agent can range from about 16% to about 24% by weight of the total composition. Other suitable thickening agents include hydroxyethyl cellulose NF, hydroxypropyl cellulose NF, hydroxypropyl methyl cellulose USP, and polyethylene oxides MW 200,000 to 7 million.
The benzocaine, preservative agents and glycol solvent agents are commercially available in NF or USP grades. The glycerin is commercially available in NF grades containing up to 4% water and the taste of the final gel product is better using the 96% glycerin.
The polyethylene glycol component of the glycol solvent system can range from PEG 400 to PEG 600. Below about PEG 400, the polyethylene glycol does not dissolve the benzocaine with ease, and above about PEG 600, the polyethylene glycol is a waxy solid and difficult to work with.
The preparation of the formulation of the invention is illustrated in the following examples. In the examples, the polyethylene glycol PEG 400 was the commercial NF grade and Carbomer 934 P brand of carboxy-vinyl polymer was that of BF Goodrich.